Confirmation of Petcock issue?

[robinelwood]

I'm just looking for some validation or redirection here; been reading past threads, and want to make sure I'm not going the wrong way.....

Bike is an 83 650L, pretty much all back to stock, other than the bars. 23k miles, new clutch, Intake boots, R/R recently done, either by me or by a local mechanic w/ a specialty in UJMs. Carbs stripped, dipped, O-ringed, et cetera.
Bike starts reliably and (now that exhuast valve 3 isn't tight) pulls like a champ. Gets some city driving 5-6 times a week.

The issue I'm having is this; Low MPG (20-30 tops), oil level rises over time-
from dead on to above the sight glass between changes-w/ some gas smell in crank case. When lifted off side stand in the morning, up to
1 teaspoon of gas dribbles from airbox drain.

Suspecting petcock,I put clear vacuum line on today; visible vapor (but no liquid) continually puffing down tube during a 50 mile ride.

SO..... am I looking at a bad petcock diaghram? Anything not fit that picture? (plugs all look fine at each check....#2 isn't fouling...) Is it worth replacing the diagphram, or should I get a new petcock? AND...past thread(s) describe getting dyna coils as making mileage much better. worth my time in this case (given that bike starts/runs reliably?)

Any advice is much appreciated. Robin Elwood (bellingham, WA)

 

[JEEPRUSTY]

DC the fuel and vacuum and check to see if there is any leakage from the taps.

Your gas can be entering by leaking past needle valve seats or by going around the O-Rings meant to seal the seats to the carb body.

maybe these rings were overlooked?

 

[robinelwood]

Thanks for response... how DC the taps? vacuum shut-off works; no visible fuel coming downfuel hose when in run; suck on vacuum line, fuel starts in fuel line.

I'll check overnight with the hoses dangled into some catch-bowls, just in case....

Is the needle seats/O rings a separate issue, or part of a petcock problem? And would bad float height adjustments be a culprit?

Thanks again, Robin

 

[Nessism]

You seem to have exonerated the petcock, so that leaves the float height or float needles leaking.

 

[tom203]

Another 650 with poor mileage? Me, I'd block off vacuum fitting at #2 carb and try just using prime setting on petcock for a few days- turn it to prime when you are running bike and remember to turn it to "on" when you ain't running.I'd also disconnect fuel line at petcock overnight.I think your petcock is dribbling fuel down some petcock line.

Why wonder ? get a new one for $45

http://www.georgefixs.com/servlet/the-148/SUZUKI-GS450,-GS650,-GS750,/Detail

 

[robinelwood]

Thank you all very much; Looks like I have some possibly conflicting avenues to pursue...

Neither hose leaked anything overnight... so, other than visible vapor in vacuum line when running, petcock seems exonerated. Still, I'll bypass the vacuum operation for a tank and see if there's a difference.

Changing out all oils today.... I'll try the O rings next. Darn carbs.

Thanks for the advice...anyone have anything good/bad to say about dyna coils on a 650l?

 

[Nessism]

Thank you all very much; Looks like I have some possibly conflicting avenues to pursue...

Neither hose leaked anything overnight... so, other than visible vapor in vacuum line when running, petcock seems exonerated. Still, I'll bypass the vacuum operation for a tank and see if there's a difference.

Changing out all oils today.... I'll try the O rings next. Darn carbs.

Thanks for the advice...anyone have anything good/bad to say about dyna coils on a 650l?

Go though them using the tutorial linked in my signature. It's easy, particularly if they are clean already.